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Single Side Band (SSB) Demodulation

Started by bangash April 4, 2007
Hello Every One!
      Actually I am working on Single Side Band (SSB)
Modulation/Demodulation. I have successfull programmed the Modulator and
the Demodulator. But Now I have one problem, that I want extract the
Carrier Frequency from the SSB (transmitted) signal at the receiver end.
Any one can guide my in the respect. 
Thanks..........................

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Hi Bangash

> Actually I am working on Single Side Band (SSB) > Modulation/Demodulation. I have successfull programmed the Modulator and > the Demodulator. But Now I have one problem, that I want extract the > Carrier Frequency from the SSB (transmitted) signal at the receiver end. > Any one can guide my in the respect.
In practice, SSB is almost always suppressed carrier, so there is no carrier transmitted. Unlike tuning an AM or FM receiver where the precise frequency is not required, for SSB-SC the receiver needs to be manually adjusted to the right frequency by the user so that it sounds right. Perhaps I haven't understood your problem properly. HTH, Howard

Howard Long wrote:


>>Actually I am working on Single Side Band (SSB) >>Modulation/Demodulation. I have successfull programmed the Modulator and >>the Demodulator. But Now I have one problem, that I want extract the >>Carrier Frequency from the SSB (transmitted) signal at the receiver end. >>Any one can guide my in the respect. > > > In practice, SSB is almost always suppressed carrier, so there is no carrier > transmitted. Unlike tuning an AM or FM receiver where the precise frequency > is not required, for SSB-SC the receiver needs to be manually adjusted to > the right frequency by the user so that it sounds right. > > Perhaps I haven't understood your problem properly.
Sometimes they deliberately leave the residue of carrier in the SSB signal (about several per cent of the original value). So the carrier can be recovered in the receiver by the use of PLL. This method was used in the professional communication systems in the old days. Vladimir Vassilevsky DSP and Mixed Signal Design Consultant http://www.abvolt.com
On Apr 5, 9:57 am, Vladimir Vassilevsky <antispam_bo...@hotmail.com>
wrote:
> Howard Long wrote: > >>Actually I am working on Single Side Band (SSB) > >>Modulation/Demodulation. I have successfull programmed the Modulator and > >>the Demodulator. But Now I have one problem, that I want extract the > >>Carrier Frequency from the SSB (transmitted) signal at the receiver end. > >>Any one can guide my in the respect. > > > In practice, SSB is almost always suppressed carrier, so there is no carrier > > transmitted. Unlike tuning an AM or FM receiver where the precise frequency > > is not required, for SSB-SC the receiver needs to be manually adjusted to > > the right frequency by the user so that it sounds right. > > > Perhaps I haven't understood your problem properly. > > Sometimes they deliberately leave the residue of carrier in the SSB > signal (about several per cent of the original value). So the carrier > can be recovered in the receiver by the use of PLL. This method was used > in the professional communication systems in the old days. > > Vladimir Vassilevsky > > DSP and Mixed Signal Design Consultant > > http://www.abvolt.com
Yes - this is a bit like vistigial sideband AM used for TVs. W.K
bangash wrote:
> Hello Every One! > Actually I am working on Single Side Band (SSB) > Modulation/Demodulation. I have successfull programmed the Modulator and > the Demodulator. But Now I have one problem, that I want extract the > Carrier Frequency from the SSB (transmitted) signal at the receiver end. > Any one can guide my in the respect. > Thanks..........................
You asked the same question about two weeks ago. Do you not believe the answers you got then? Jerry -- Engineering is the art of making what you want from things you can get. &macr;&macr;&macr;&macr;&macr;&macr;&macr;&macr;&macr;&macr;&macr;&macr;&macr;&macr;&macr;&macr;&macr;&macr;&macr;&macr;&macr;&macr;&macr;&macr;&macr;&macr;&macr;&macr;&macr;&macr;&macr;&macr;&macr;&macr;&macr;&macr;&macr;&macr;&macr;&macr;&macr;&macr;&macr;&macr;&macr;&macr;&macr;&macr;&macr;&macr;&macr;&macr;&macr;&macr;&macr;&macr;&macr;&macr;&macr;&macr;&macr;&macr;&macr;&macr;&macr;&macr;&macr;&macr;&macr;&macr;&macr;
Vladimir Vassilevsky wrote:
> > > Howard Long wrote: > > >>> Actually I am working on Single Side Band (SSB) >>> Modulation/Demodulation. I have successfull programmed the Modulator and >>> the Demodulator. But Now I have one problem, that I want extract the >>> Carrier Frequency from the SSB (transmitted) signal at the receiver end. >>> Any one can guide my in the respect. >> >> >> In practice, SSB is almost always suppressed carrier, so there is no >> carrier transmitted. Unlike tuning an AM or FM receiver where the >> precise frequency is not required, for SSB-SC the receiver needs to be >> manually adjusted to the right frequency by the user so that it sounds >> right. >> >> Perhaps I haven't understood your problem properly. > > Sometimes they deliberately leave the residue of carrier in the SSB > signal (about several per cent of the original value). So the carrier > can be recovered in the receiver by the use of PLL. This method was used > in the professional communication systems in the old days. > > Vladimir Vassilevsky > > DSP and Mixed Signal Design Consultant > > http://www.abvolt.com
If I recall correctly such systems are designated as residual carrier SSB, or pilot carrier SSB, or some such. -- Tim Wescott Wescott Design Services http://www.wescottdesign.com Posting from Google? See http://cfaj.freeshell.org/google/ Do you need to implement control loops in software? "Applied Control Theory for Embedded Systems" gives you just what it says. See details at http://www.wescottdesign.com/actfes/actfes.html
Howard Long wrote:
> Hi Bangash > >> Actually I am working on Single Side Band (SSB) >> Modulation/Demodulation. I have successfull programmed the Modulator and >> the Demodulator. But Now I have one problem, that I want extract the >> Carrier Frequency from the SSB (transmitted) signal at the receiver end. >> Any one can guide my in the respect. > > In practice, SSB is almost always suppressed carrier, so there is no carrier > transmitted. Unlike tuning an AM or FM receiver where the precise frequency > is not required, for SSB-SC the receiver needs to be manually adjusted to > the right frequency by the user so that it sounds right. > > Perhaps I haven't understood your problem properly. > > HTH, Howard > >
In theory, if it's voice over SSB that's being transmitted, you can automatically fine tune the SSB receiver. This works (purportedly) because the vocal cords generate a comb of frequencies, which the vocal tract shapes. So you can do an FFT, then extract the virtual zero point of the comb, then servo to it. There was an article in QEX on this technique years ago. I suspect that it doesn't really work all that well, because I don't see any amateur radio receivers being sold with automatic fine tuning on SSB. -- Tim Wescott Wescott Design Services http://www.wescottdesign.com Posting from Google? See http://cfaj.freeshell.org/google/ Do you need to implement control loops in software? "Applied Control Theory for Embedded Systems" gives you just what it says. See details at http://www.wescottdesign.com/actfes/actfes.html
Tim Wescott <tim@seemywebsite.com> writes:

> Howard Long wrote: >> Hi Bangash >> >>> Actually I am working on Single Side Band (SSB) >>> Modulation/Demodulation. I have successfull programmed the Modulator and >>> the Demodulator. But Now I have one problem, that I want extract the >>> Carrier Frequency from the SSB (transmitted) signal at the receiver end. >>> Any one can guide my in the respect. >> In practice, SSB is almost always suppressed carrier, so there is no >> carrier transmitted. Unlike tuning an AM or FM receiver where the >> precise frequency is not required, for SSB-SC the receiver needs to >> be manually adjusted to the right frequency by the user so that it >> sounds right. >> Perhaps I haven't understood your problem properly. >> HTH, Howard > In theory, if it's voice over SSB that's being transmitted, you can > automatically fine tune the SSB receiver. This works (purportedly) > because the vocal cords generate a comb of frequencies, which the > vocal tract shapes. So you can do an FFT, then extract the virtual > zero point of the comb, then servo to it. > > There was an article in QEX on this technique years ago. I suspect > that it doesn't really work all that well, because I don't see any > amateur radio receivers being sold with automatic fine tuning on SSB.
Assuming cos[(omega+delta)*t] is your LO, then couldn't you try simply adapting the tuning until the energy in sin[(omega+delta)*t]*x(t) is minimum (ideally, zero)? This is from the idea that, if the tuning is correct, there will be no imaginary component in a quadrature downconversion. This is from the hip, so I could be out in left field. -- % Randy Yates % "How's life on earth? %% Fuquay-Varina, NC % ... What is it worth?" %%% 919-577-9882 % 'Mission (A World Record)', %%%% <yates@ieee.org> % *A New World Record*, ELO http://home.earthlink.net/~yatescr
On Fri, 06 Apr 2007 13:04:53 -0400, Randy Yates <yates@ieee.org>
wrote:

>Tim Wescott <tim@seemywebsite.com> writes: > >> Howard Long wrote: >>> Hi Bangash >>> >>>> Actually I am working on Single Side Band (SSB) >>>> Modulation/Demodulation. I have successfull programmed the Modulator and >>>> the Demodulator. But Now I have one problem, that I want extract the >>>> Carrier Frequency from the SSB (transmitted) signal at the receiver end. >>>> Any one can guide my in the respect. >>> In practice, SSB is almost always suppressed carrier, so there is no >>> carrier transmitted. Unlike tuning an AM or FM receiver where the >>> precise frequency is not required, for SSB-SC the receiver needs to >>> be manually adjusted to the right frequency by the user so that it >>> sounds right. >>> Perhaps I haven't understood your problem properly. >>> HTH, Howard >> In theory, if it's voice over SSB that's being transmitted, you can >> automatically fine tune the SSB receiver. This works (purportedly) >> because the vocal cords generate a comb of frequencies, which the >> vocal tract shapes. So you can do an FFT, then extract the virtual >> zero point of the comb, then servo to it. >> >> There was an article in QEX on this technique years ago. I suspect >> that it doesn't really work all that well, because I don't see any >> amateur radio receivers being sold with automatic fine tuning on SSB. > >Assuming cos[(omega+delta)*t] is your LO, then couldn't you try simply adapting >the tuning until the energy in sin[(omega+delta)*t]*x(t) is minimum (ideally, >zero)? This is from the idea that, if the tuning is correct, there will be >no imaginary component in a quadrature downconversion. > >This is from the hip, so I could be out in left field.
That's a crude way to describe a phase detector, so I'd think it'd work. The only thing missing is that the sign of the error (not just the magnitude) is really needed for tracking or it'll hunt to find the right direction to correct. Eric Jacobsen Minister of Algorithms Abineau Communications http://www.ericjacobsen.org